Over the past several years, laparoscopy has become an important means for conducting minimally invasive surgery. Because trauma to the patient is greatly reduced, as compared with traditional invasive surgical techniques, patient discomfort and post-operative recovery time are greatly reduced.
Laparoscopic surgery utilizes elongated, hollow tubes called cannulae both to deliver and remove fluids from the site to be operated upon. In the case of fluid delivery, it is highly desirable to control both the flow rate and the force with which the fluid is carried to the surgical site. A variety of valves have been employed to achieve this desired control.
Valves currently used in conjunction with laparoscopic surgery comprise two basic styles, one employing a hole through the piston through which fluid passes, the other employing an hourglass-style piston with the fluid traversing around the waist of the hourglass.
Existing valve styles employ a metal housing surrounding a metal piston that moves up and down through the housing. The valve components are manufactured with close mechanical tolerances and require extensive lubrication in order to avoid jamming or sticking during operation. Such valves lack any sealing means, other than the seal provided by the lubricated contact of the piston with the valve housing.
Recently, laparoscopic techniques have come to depend upon the delivery of fluids at relatively high pressure. Known valves, such as those described, suffer several drawbacks when used to deliver fluids under high pressure. First, and most importantly, such valves leak extensively because there are no seals. Second, with some types of metallic valves, such as those fabricated from brass, the metallic surfaces of the piston and the housing oxidize to form extensive residue. Accumulated residue often causes the valves to stick or "freeze up". Finally, because the valve components are tooled to such narrow tolerances, they must be meticulously cleaned and relubricated after each use. Failure to carry out such procedures also results in valve failure.
Given the limitations of valves currently used for surgical applications, it is desirable to have a valve that is simple, easy to disassemble and clean, reliable, and would operate leak free under high pressures and with pressure gradients in either direction.